The present invention relates to a compact electronic calculator having a graph display function for displaying a graph of any functional formula.
A conventional compact electronic calculator is known which can display the graph of a functional formula. In an electronic calculator of this type, a given functional formula y=f(x) is keyed in and the value of dependent variable y is calculated for each value of independent variable x.
More specifically, when independent variable x is changed in units of 0.5 within a range of 0 to 10, independent variable x and formula f(x) must be input twenty times each, which is a very cumbersome operation.
Conventional electronic calculators can only display graphs of formulas at the display section. Since the coordinate axes are not displayed, it is difficult to determine the number of roots and their values.
In addition, coordinates which fall outside the display region for variables x and y are not connected with lines. Therefore, graph portions at the boundary of the display region become discrete and do not provide a complete graph, this resulting in an incomplete visual display.
In a conventional general function electronic calculator, only numerical information can be processed. If a visual graph image is desired for even a simple function such as a sine function, numerical information must be manually plotted on graph paper.
With computers some graph displays can be obtained with programs. However, a computer must have a programming capability to provide this function. Even if this function is provided, various complex input procedures are required including setting of a display range or coordinates.
In a conventional computer having a graph display function, a program for drawing a graph can be created with a personal computer or the like, and data is input to allow a display unit to display a graph.
However, in this case, a special graph program must be created by the operator.
Since only one display buffer is conventionally used for the display screen, when a graph formula or a comment is to be added to the graph, it is inserted in the graph image. This results in overlapping of the characters and graph and poor readability.